[cssom-view] elementFromPoint, elementsFromPoint, and caretPositionFromPoint should not return an element inside a shadow tree #556
Description
elementFromPoint and elementsFromPoint should not return an element inside a shadow tree. Instead, it should look for the highest shadow host of the element and return that instead so that it doesn't leak an element in shadow trees.
See the shadow DOM specification.
More precisely, once these methods are added on DocumentOrShadowRoot interface, then we need to retarget the element we found against the context object.